As an example of the use of a diminished spark for black powder ignition, black powder cartridges, 45-70 cal for example,employ a paper disc in the case over the primer vent before the powder is poured in. Alternately, a disc of paper is placed inside the primer cup in the base of the cartridge to accomplish the same thing. It has to do with increased accuracy.
Sorry for the mention of cartridges, it was meant to be an example of how a reduced flame works better for black powder ignition. Garbage this post if it offends.